224 



PORIFERA. 



the other or excurrent from the ampullae to the cloaca, the two 

 being connected by the ampullae alone. Both may consist of lacunar 

 spaces (fig. 164), or have a more regular arrangement (fig. 165), 



FIG. 165. Section of cortex of Chondrilla nucula, the skeleton omitted. (After Schulze.) 

 c 1 , afferent canals; c 2 , efferent canals; <;, ampullae; m, cloaca; o, osculum. 



the canals from the pores uniting in trunks and these in turn 

 branching to go to the ampullae. The excurrent canals also show 

 -a similar tree-like arrangement. Not infrequently extensive 

 subdermal or subcloacal spaces occur. The relations may be more 

 complicated by the development of several cloacae, or these may be 



FIG. 166. FIG. 167. 



FIG. 166. Surface view of dermal pores of Aplysina aerophobia, (After Schulze.) 

 FIG. 167. Ascyssa acufera.^ (After Haeckel.) 



repressed; again by the branching of the sponge (fig. 167), while 

 still further the branches may anastomose (fig. 168), giving rise to 

 a network. 



Sponges may reproduce asexually, small portions separating as 

 buds and producing new animals. Usually sexual reproduction 

 prevails. Eggs and spermatozoa arise from mesoderm cells (fig. 

 162), are fertilized and undergo segmentation at the point of origin, 

 and leave the parent as flagellate larvae (fig. 169, A). At fixation 



